1. Field of the Invention
The present invention relates to ink suited for ink-jet recording and an ink-jet recording process employing the ink. More particularly, it relates to ink having a good long-term storage stability and achieving a good water resistance of records, and an ink-jet recording process employing it.
2. Description of the Related Art
In ink-jet recording methods, ink droplets are formed according to various ink ejection methods (for example, known are an electrostatic attraction method, a method in which a mechanical vibration or displacement is applied to ink with use of a piezoelectric device, a method in which ink is heated to utilize the pressure thereby produced, etc.), and a part, or the whole, thereof is adhered on a recording medium such as paper to effect the recording.
As for the ink to be used, chiefly employed is a process of carrying out the recording by use of a recording liquid (also called an ink) mainly comprised of water and a water-soluble organic solvent and in which a dye is dissolved.
In the recording process carried out by use of the ink of this type, the items required to be satisfied may somewhat differ depending on the recording method, but what are most important as the items commonly required to be satisfied are that;
(1) no feathering occurs and recorded images of good quality can be obtained;
(2) ink can be fixed rapidly;
(3) prints have excellent fastness such as water resistance, light-fastness or the like;
(4) nozzles and ink pathway are not clogged with ink;
(5) stable ejection can be achieved for a long period of time;
(6) ink may undergo no change even after its storage for a long period of time; etc.
To satisfy a part of, or the whole of, the above objects, studies have been actively carried out from both viewpoints of apparatus and ink, and considerable effect has been realized depending on what performance is required.
However, since most part of the conventional aqueous ink as mentioned above is held by those in which a direct dye or an acid dye is used as a dye, there may arise a problem in various kind of fastness, particularly the water resistance, when the recording is carried out by an ink-jet recording method, particularly when paper or cloth having a recording face on which fibers are exposed is used as a recording medium.
To cope with this problem, a great number of proposals have been made regarding employment of aqueous inks of a pigment dispersion type (for example, Japanese Patent Laid-open Publication No. 147859/1981). According to these method, the fastness of records can be satisfied to a certain extent, but the problem of clogging of nozzles occurring when such inks are used for ink-jet recording and the problem in the storage stability of ink may become considerably serious as compared with the conventional ink of the dye dispersion type.